Numerous people in the last 50 years have been involved in technological efforts to generate electricity from sunlight. Some have mounted photovoltaic panels on sun-tracking swivels. Others have concentrated great amounts of sunshine on solar power towers that boil steam. Still others have concentrated sunshine on pipes filled with oil, which heats the oil to 800° Fahrenheit, where this heat eventually turns water into steam, which drives an electric turbine. Some have used solar heat to power Stirling engines.
One problem with boiling water by solar methods to create steam is achieving a 100° Celsius minimum boiling temperature. Numerous low-grade energy sources exist, including waste steam from solar power plants and from industrial plants, low-grade geothermal heat deposits, and surface air just above parking lots.
A 600 foot high, 30 foot diameter vertical solar chimney was built in Manzares, Spain. 11 acres of plastic on poles were deployed around the chimney. Each sunny day, air under the plastic grew hot. The hot air flowed up the chimney. The chimney had a strong enough draft that a wind turbine inside the chimney generated 50 kilowatts on each sunny day. Unfortunately, the cost of building the 600 foot tower made this particular electricity installation economically unusable. Also, the 600 foot tower was a minor aviation hazard.
The Manzares concept of gathering and heating local air by erecting a huge acreage of plastic sheets on 10 foot poles is seen as relatively expensive. The experiment's flat plastic sheeting appears to have been vulnerable to hail, to rain buildup and pondage on top of the plastic, to high wind damage and to rare snow accumulation. In addition, some commonly used plastics such as polyvinyl chloride will deteriorate in the sun's rays within 4 years.
A 3000 foot solar chimney was proposed in Australia. With greater elevation, the efficiency of the solar chimney would rise more than proportionally with height. Unfortunately, the cost of building a 3000 foot tall structure also rises more than proportionally with height. Cost versus benefits killed this project.
An inexpensive diagonal chimney up a mountainside was built and used in the 1900s to channel noxious fumes out of a northern New England valley from a smelting operation in the valley. A small rectangular trench was dug up the side of the valley to a ridge top, and the trench was lined and covered with slate stones. Hot air flowed from a smelter diagonally up the in-ground chimney to the ridgeline, at which point the noxious fumes blew away. The height of this chimney, hundreds of feet in elevation gain, was irrelevant to the builders, as the whole of the chimney rested on an existing mountainside.
U.S. Pat. No. 3,436,908, filed by V. VanDelic, describes a solar heat-powered diagonal chimney.
U.S. Pat. No. 4,367,627, filed by Gisberto Pretini of Pisa, Italy, describes a diagonal chimney used with a heat collection method and an air-turned turbine at the base of the chimney, used for power generation.
U.S. Pat. No. 7,026,723, filed by Mauricio Rodolfo Moreno of Santiago, Chile, describes a solar heat powered diagonal chimney traveling more than 1000 meters in elevation up a mountainside, which is used simultaneously for removing smog from a smoggy valley, and for generating electricity at the base of the diagonal chimney. With a smog-reducing diagonal chimney, asthma casualties in the valley are then reduced and people are better able to exercise outdoors. Air temperatures across the valley are reduced. The valley's humidity is reduced. Outside air becomes more breathable without first air conditioning the air, so that regional air conditioning needs are reduced. Overall, the valley becomes a nicer place to live.
This patent's author holds another U.S. Pat. No. 8,408,199, “Solar Reflector, Collecting Window and Heat Storage”. That patent's reflector and target window design has advantages that will work in a number of solar applications, including the heating of air and water in feeder tubes leading toward the lower end of a solar chimney. Specifically, the reflector inexpensively concentrates heat, allowing for higher heat generation than with unconcentrated solar heating, with less heat loss at night and on cloudy days, the target window line is oriented to be shielded from rain and other weather problems, and the enclosure behind a line of target windows can maintain an air pressure differential for shipping a stream of air.